Kensaku Kinoshita

A simple assay for measurement of urinary p-aminobenzoic acid in the oral pancreatic function test

Abstract A simple method for the measurement of p -aminobenzoic acid (PABA) in urine following oral administration of N -benzoyl- l -tyrosyl- p -aminobenzoic acid (Bz-ty-PABA), a synthetic peptide used for the assessment of exocrine pancreatic function, was investigated using p -dimethylamino cinnamaldehyde (DACA) as a chromogenic reagent. DACA reacted with PABA in acidic solution and the red dye which developed had an absorption spectrum with maximum at 550 nm. Urine containing PABA and its conjugated metabolites was hydrolyzed with HCl, DACA solution was added to a portion of the hydrolysate, and the color intensity was determined. When Bz-ty-PABA was administered orally to healthy humans and patients with pancreatic insufficiency, urinary PABA content determined by the DACA method was in good agreement with that by the diazo-coupling method. This DACA method is preferable to the diazo-coupling method with respect to the simplicity and rapidity of the procedure and to the stability of the reagent solution. It is especially useful for the above application in the clinical laboratory.

The metabolic fate of 4-amino-2-(4-butanoyl-hexahydro-1H-1, 4-diazepin-1-y1)-6, 7-dimethoxy-quinazoline HCI

1. 4-Amino-2-(4-butanoyl hexahydro-1H-1, 4-diazepin-1-yl)-6, 7-dimethoxy [2-14C]quinazoline HCl (14C-DDQ) is rapidly absorbed in rats and rabbits and excreted mainly into faeces via the bile. 2. The main metabolites in tissues and excreta are O- and N-glucuronides of 7-O-desmethyl DDQ in rats and the N-glucuronide of DDQ in rabbits. 3. Significant enterohepatic circulation of the metabolites occurs in rats. 4. The absorption of DDQ is also rapid in healthy humans and the plasma concentration decreases with an apparent half-life of 1 . 53h.

Identification of urinary and microsomal metabolites of geranylgeranylacetone in rats.

The metabolic disposition of the anti-ulcer agent geranylgeranylacetone (GGA) was examined in rats. Urinary metabolites were isolated and identified by mass spectrometry and 1H n.m.r. studies. Three metabolites were dicarboxylic acids with chain lengths of C7, C9 and C11 and accounted for 31.6%, 14.8% and 5.3%, respectively, of the radioactivity excreted in the urine 24 h after oral administration of 14C-GGA. The metabolites produced by the incubation of GGA with liver microsomes in the presence of an NADPH-generating system were identified as an omega-hydroxylated derivative of GGA and its ketone-reduced form. The characterization of GGA metabolites indicates that the metabolic pathway of GGA in rats involves omega-oxidation (possibly via the corresponding carboxylic acid) and successive beta-oxidation processes.

Incorporation of radioactivity into amino acids and fatty acids after administration of 14C-geranylgeranylacetone to rats.

The radioactive components present in plasma proteins and adipose tissue after oral dosing of 14C-geranylgeranylacetone (GGA) to rats were characterized by gel filtration, paper electrophoresis, t.l.c. and reversed-phase column chromatography. The radioactivity associated with the plasma proteins was identified as 14C-labelled amino acids (Glu, Asp, Ala, Pro, Gly and probably Ser); however, no 14C was detectable in the essential amino acids. Radioactivity accumulated in adipose tissue as 14C-labelled fatty acids of triglycerides. The incorporation of 14C into amino acids and fatty acids may be due to the formation of 14C-propionyl-CoA resulting from omega-oxidation and successive beta-oxidations of 14C-GGA. This view was supported by the finding that 14C-acetate was incorporated into amino acids and fatty acids in a similar manner to 14C-GGA.

Determination of tripamide and its metabolites in plasma, red blood cells and urine by high-performance liquid chromatography

A procedure for the determination of tripamide and its hydroxylated metabolites in plasma, red blood cells and urine by reversed-phase high-performance liquid chromatography is described. The concentrations in red blood cells showed a monophasic decline and the half-life was 9.5 h. The concentration in red blood cells was markedly higher than that in plasma, showing that 95-98% of the drug is present in whole blood, after a dose of tripamide (90 mg) in man. The specificity and sensitivity of this procedure appear to be satisfactory for pharmacokinetic studies.

Studies of metabolism of tripamide, a new antihypertensive agent. II. Metabolism by the hepatic microsomal enzymes

1. The metabolism of tripamide, N-(4-aza-endo-tricyclo[5.2.1.0(2.6)]decan-4-yl)-4-chloro-3-sulphamoylbenzamide, has been studied with rat liver microsomal preparations. 2. Hydrolysis of tripamide was induced by phenobarbitone pretreatment and inhibited by O-ethyl O-p-nitrophenyl phenylphosphonothioate (EPN), a classical inhibitor of hepatic microsomal arylamidase. The hydrolysis was also catalysed by partially purified rabbit liver microsomal arylamidase. 3. The hydroxylation of tripamide was induced by 3-methylcholanthrene and inhibited by CO. 4. Inhibition of the hydroxylation of tripamide by antibodies of cytochrome P-450 and P-448 was studied. The 8-hydroxylation was inhibited by both antibodies, but 3-hydroxylation was inhibited by neither.